Science - Chemistry - General Chemistry - 1 Properties of
materials (P7150300)
1.3 Properties of matter - boiling point
Experiment by: Phywe
Printed: Oct 11, 2013 1:23:01 PM
interTESS (Version 13.06 B200, Export 2000)
Task
Task
How can substances be differentiated? (3)
Determine the boiling point of water and of different table salt solutions.
Use the space below for your own notes.
Logged in as a teacher you will find a button below for additional information.
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Additional information
Learning objectives
• Using the boiling point, substances can be accurately identified.
• Contaminated substances have a different boiling point than the respective pure
substances.
• Different concentrations of a solution of the same substance have different
boiling points.
Notes on set-up and procedure
Prepare the required quantities of salt (10 g; 20 g; 30 g) beforehand.
Ensure that the holes and the other glass-rubber connections are lubricated with
glycerol. Inform the students that, especially on inserting the thermometer, force
should not be used because the glass items will otherwise break. Instruct the students
in the use of the burner.
Hazards
•
•
•
•
Lubricate rubber-glass connections with a drop of glycerol!
Above all, do not use force to insert the thermometer!
To avoid delayed boiling add fresh boiling stones (beads) to the liquid!
Wear protective glasses!
Note
Do not use quantities of salt greater than 25 g per 100 ml water, since larger quantities
do not dissolve completely. The values given in the tables are exemplary values.
Remarks on the method
When performing the two experiments, it is advisable to work in small groups and
evaluate the experiments together. This can be put into practice as early as the
determination of the boiling point of water by determining the mean value of the
boiling temperature found by the groups. In particular, however, when determining
the correlation between concentration and boiling point of a solution, the students
should work in small groups. In this case, ensure that the students use quantities of
water which are as equal as possible. By doing this, the linearity of the correlation
between boiling point elevation and the quantity of salt becomes apparent.
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Suggestions for advanced classes
The second part of the experiment is also suitable for the determination of the molar
boiling point elevation of water. To do this, the quantities of sodium chloride used
must be converted to molar variables. In this case, the elevation of the boiling point
should be measured for 100 ml of water. Then a value of 5.2 °C per mol of dissolved
ions results.
Waste disposal
The salt solutions can be poured into the container for acids and alkalis.
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Material
Material from "TESS advanced Chemistry Set General Chemistry, CH-1" (Order
No. 15300-88)
Position No. Material
Order No. Quantity
1
Protective glasses, clear glass
39316-00
1
1
Wire gauze, 160 × 160 mm, ceramic cen.
33287-01
1
2
Support rod, stainless steel, l = 400 mm
02039-00
1
3
Bosshead
02043-00
1
3
Support ring, i.d. 100 mm, with clamp
37701-01
1
4
Support base, variable
02001-00
1
5
Universal clamp
37715-00
1
6
Wash bottle, 250 ml
33930-00
1
7
Erlenmeyer flask, Duran, 100 ml, PN 29
36428-00
1
8
Rubber stopper, d = 32/26 mm, 2 holes
39258-02
1
9
Glass tube, right-angled, I = 60+85 mm, 1 p.
36701-52
1
9
Stopwatch
24025-00
1
Lab thermometer, -10..+150 °C
38058-00
1
10
Chemicals, additional material
Position No. Material
Order No. Quantity
Bunsen burner, natural gas, DIN
46917-05
1
Safety gas tubing, DVGW
39281-10
1
Glycerol, 99%, 250 ml
30084-25
Sodium chloride, 250 g
30155-25
Beads, 200 g
36937-20
Water
Material required for the experiment
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Setup
Setup
Hazards
• Lubricate rubber-glass connections with a drop of glycerol! In particular, do not use force
to insert the thermometer!
• To avoid delayed boiling, add fresh boiling stones (beads) to the liquid!
• Wear protective glasses!
Set-up
Set up a stand with the support base and the support rod as you can see in Fig. 1 and Fig. 2.
Fig. 1
Fig. 2
Attach the support ring to the support rod (Fig. 3) and place the wire gauze onto the ring
(Fig. 4).
Fig. 3
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Fig. 4
Attach the Erlenmeyer flask to the support rod in such a manner that its bottom is in contact
with the wire gauze (avoid tension) as you can see in Fig. 5 - Fig. 7.
Fig. 5
Fig. 6
Fig. 7
Half-fill the Erlenmeyer flask with water (Fig. 8) and add three beads (Fig. 9).
Fig. 8
Fig. 9
Insert the thermometer into one hole of the rubber stopper (Fig. 10) after you have lubricated
it with a drop of glycerol. While doing so, hold the thermometer vertically; do not use force.
Insert the right-angled glass tube into the other hole in the stopper in a similar manner (Fig.
11).
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Fig. 10
Fig. 11
Seal the Erlenemeyer flask with the thus prepared stopper (Fig. 12); shift the thermometer
downward such that it is immersed approximately 3 cm deep in the water.
Fig. 12
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Action
Action
Procedure
Heat the water cautiously with the burner until it begins to boil (Fig. 13). Now, measure the
temperature every thirty seconds for five minutes and record the values in Table 1.
Fig. 13
Extinguish the burner's flame. Allow the water to cool slightly; open the Erlenmeyer flask (Fig.
14); pour the salt which the teacher has distributed into the water (Fig. 15) and reseal the flask.
Reheat the water to boiling and measure the boiling point as above.
Fig. 14
Waste disposal
The salt solutions can be poured into the container for acids and caustic solutions.
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Fig. 15
Evaluation
Evaluation
Question 1:
Record the measured boiling temperatures of the water in Table 1.
Table 1. Boiling point of water
Measurement
Time in sec
Temperature in °C
1
Incipient boiling
nnnnnnnnnn
2
30
nnnnnnnnnn
3
60
nnnnnnnnnn
4
90
nnnnnnnnnn
5
120
nnnnnnnnnn
6
150
nnnnnnnnnn
7
180
nnnnnnnnnn
8
210
nnnnnnnnnn
9
240
nnnnnnnnnn
10
270
nnnnnnnnnn
11
300
nnnnnnnnnn
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Table 1. Boiling point of water
Measurement
Time in sec
Temperature in °C
1
Incipient boiling
97
2
30
98
3
60
99
4
90
100
5
120
100
6
150
99
7
180
100
8
210
101
9
240
100
10
270
99
11
300
100
Question 2:
Record the measured boiling points for the quantity of salt which you received in Table 2.
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Table 2. Boiling point of the salt water solutions
Measurement
Time in sec
Temperature in °C
10 g of salt
1
Incipient boiling nnnnnnnnnn
20 g of salt
30 g of salt
nnnnnnnnnn
nnnnnnnnnn
2
30
nnnnnnnnnn
nnnnnnnnnn
nnnnnnnnnn
3
60
nnnnnnnnnn
nnnnnnnnnn
nnnnnnnnnn
4
90
nnnnnnnnnn
nnnnnnnnnn
nnnnnnnnnn
5
120
nnnnnnnnnn
nnnnnnnnnn
nnnnnnnnnn
6
150
nnnnnnnnnn
nnnnnnnnnn
nnnnnnnnnn
7
180
nnnnnnnnnn
nnnnnnnnnn
nnnnnnnnnn
8
210
nnnnnnnnnn
nnnnnnnnnn
nnnnnnnnnn
9
240
nnnnnnnnnn
nnnnnnnnnn
nnnnnnnnnn
10
270
nnnnnnnnnn
nnnnnnnnnn
nnnnnnnnnn
11
300
nnnnnnnnnn
nnnnnnnnnn
nnnnnnnnnn
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Table 2. Boiling point of the salt water solutions (Exemplary values)
Measurement
Time in sec
Temperature in °C
10 g of salt 20 g of salt 30 g of salt
1
Incipient boiling
102
102
103
2
30
103
105
107
3
60
104
106
110
4
90
104
107
111
5
120
105
108
112
6
150
105
107
111
7
180
104
107
111
8
210
105
107
112
9
240
105
108
111
10
270
104
107
111
11
300
105
107
111
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Questions and exercises
Questions and exercises
Question 1:
Explain the course of the curve in chart 1.
The curve rises until it reaches the highest value, the boiling point. The boiling point
of water is 100 °C.
Oscillations arround the boiling point result from the non-uniform application of
energy. The exact measured value is a function of the air pressure.
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Question 2:
Plot the values for the other quantities of salt obtained by the other experimental groups in
Table 2.
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See Table 2.
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Question 3:
Calculate the mean of the boiling points for the respective salt solutions.
Table 3.
salt in g
mean values in °C
0
nnnnnnnnnn
10
nnnnnnnnnn
20
nnnnnnnnnn
30
nnnnnnnnnn
Table 3a
salt in g
mean values in °C
0
100
10
104
20
107
30
111
Question 4:
Evaluate the results of Chart 3 and state the correlation concisely in writing.
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A salt solution has a different boiling point than pure water. The more salt dissolved
in water, the higher the boiling point.
Concise statement: Solutions have a different boiling point than the pure solvent. The
higher the concentration of the dissolved substance, the higher the boiling point.
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Question 5:
What change in the state of aggregation occurs in the substances on boiling? Name the opposite
process, complete the state diagramm (Fig. 18).
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Transition from liquid to gas: evaporation
Transition from gas to liquid: condensation
Fig. 18
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